Plena Libre is one of Puerto Rico's most popular bands, a group marked by its dynamic rhythms, passionate singing, powerful horn section, imaginative choreography and the inventive arrangements of bandleader and bass player Gary Nuñez. Plena Libre's irresistible groove turns every gig into a party, and its international success is a source of great cultural and national pride on the island.

Since they began playing together in 1994, the band members have revitalized Puerto Rican folk and popular music. Today, plena is recognized as one of the great tropical grooves, equal to the son of Cuba, Dominican merengue and Brazilian samba.

"Plena is a rhythm, a dance and a style of music," Nuñez says, his voice full of the energy and enthusiasm that infuses his music. "When we play outside of Puerto Rico, we teach the audience a few basic steps. Plena is easy to dance to, and you can do it alone, with a partner or in a group. It's great to see the audience getting into it."

When you see Plena Libre rocking the house, it's hard to believe that less than a decade ago plena, bomba and other typical folkloric Puerto Rican rhythms were on the verge of extinction. In the '70s and '80s, despite the success artists such as Willie Colon and Mon Rivera had with the form, most young people weren't interested in traditional music. Plena was played at festivals and on holidays, but was losing its vitality.

"Plena is the youngest Puerto Rican rhythm," Nuñez says. "It's barely 100 years old. It's one of the four main types of music that constitute the essence of Puerto Rican music: plena, bomba, danza and country music. Our rhythms are built on three influences: Native American, Spanish and African.

"What we got from the Indians is the hardest to trace because most of their culture was wiped out or adopted by the Spanish. There's some vocabulary and the guicharo, a gourd with ridges cut into it, which is a common rhythm instrument in the Caribbean. Cubans call it a guiro, but the sound of our guicharo is very different. The plena and bomba are the most African of our rhythms, based on intricate drum patterns. Traditionally, the plena ensemble was three panderos (hand drums similar to tambourines but without the tiny cymbals), a guicharo, a lead singer and a chorus that responded to the lead singer. The lyrics were usually topical and often improvised.

"(Plena) singers had to have a lot of musical skill and a big vocabulary. As a song unfolded and the musicians began improvising on the melody, the singer had to keep up, inventing new lyrics, making sure they were all in meter and complementary to the melodies. It's like an instrumental solo, but the singer has the added complication of the words.

"Plena was called the oral newspaper; it gave poor people a chance to comment on the events of everyday life with a humorous or satiric edge, and the songs are an important part of our history. But a few years ago, the plena got stuck. People were still singing old lyrics; they weren't relevant to the new generation. I wanted to change that. I figured I could take plena to other cultures to get people interested in the music of Puerto Rico.

"When I started exploring the folkloric music of Puerto Rico, I discovered most of the (chord) progressions you find in jazz, you can find in Puerto Rican traditional music. With Plena Libre, I wanted to keep the folkloric root as a blueprint and infuse it with contemporary music to build a sound that would be exciting to younger audience members. Every generation has the duty to develop and change folk music; that's what keeps the music alive. In Plena Libre, we still do some songs the traditional way -- just percussion and voice. We don't want the audience to forget where we're coming from. My work as a composer and arranger is to find new avenues for plena. That's why the band is called Plena Libre. Libre means free, so I'm always experimenting to satisfy my curiosity and push the envelope as far as I can."

When he was younger, Nuñez wanted to play jazz, but Puerto Rican music was always in the background, calling him with its siren song.

"My mom was a home singer with a beautiful voice, and my middle brother was a singer who loved Latin music," he says. "I heard Dizzy (Gillespie), Miles (Davis) and Cal Tjader when I was 8 or 10 and started piano at 12. I discovered Puerto Rican music at 21, but I wanted to know as much about music from the rest of the world as I could learn.

"I taught myself guitar, bass, vibes, congas, timbales and finally went to the Puerto Rican Conservatory of Music, surprising myself by graduating magna cum laude. In the '70s, I was in Moliendo Vidrio, a folkloric band that was the foundation for what I'm doing today.

"We played music from the Puerto Rican countryside, as well as plena and bomba in a more traditional style. I did the arrangements and played bass and cuatro (the Puerto Rican lute that has five pairs of double strings and sounds like a cross between a 12-string guitar and a mandolin.)

"In the '80s, I started Caribe Jazz to play plena and bomba with a Latin jazz flavor but gave that up to start Plena Libre in '94. I was just jamming with a couple of musicians at first, but the group came together quickly. It was like a Cinderella story. In less than six months, we were gigging. Then we made an album, 'Juntos y Revueltos,' and won every possible award in Puerto Rico."

Nuñez raised the money to produce "Juntos y Revueltos" independently, which was a big risk.

"It was unusual because the big labels control everything," he says. "At first, the album was sold mostly at our shows. Radio wouldn't touch it, but the fans pushed the radio stations to play it. I was amazed at the phenomenon, so I have to put out a thank you to our audience in big letters."

Since that opening salvo, Plena Libre has become an international sensation with multiple Grammy nominations and fans around the world. The band has revitalized plena and called attention to the rich folkloric traditions of Puerto Rico.

"When I started Plena Libre, there weren't many groups (doing plena)," Nuñez says. "Because I added bass, keyboards, timbales, congas and trombones, there was some controversy, most of it coming from the strict folkloric guys. But there are two ways of looking at the world: You either stick to what you have, or you use what you have in order to create and develop as a person, a nation or a musician. I prefer the people who try to develop and take risks and create something new. My career is based on that. If you take a risk, you may not get it right all the time, but your spirit is in a constant search for new things. You want to say to yourself and the rest of the world, 'I'm not only what I am, but what I can be.' "